Process for preparing high molecular weight aliphatic carboxylic acids by chromosulfuric acid oxidation of {60 -olefins

ABSTRACT

In the oxidation of higher Alpha -olefins by means of chromosulfuric acid the corresponding saturated higher aliphatic monocarboxylic acids are obtained in a high yield, if the oxidation is carried out in the presence of from 2 to 15 % by weight of saturated, aliphatic mono- or dialcohols having from 10 to 40 carbon atoms. The carboxylic acids obtained are suitable for preparing wax-like substances.

United States Patent Schmidt et al. 1 Dec. 2, 1975 [54] PROCESS FOR PREPARING HIGH 2,470,515 5/1949 Myers ct a1. 260/413 MOLECULAR WEIGHT ALIPHATIC 2,644,837 7/1953 Schweitzer 1 260/484 CARBOXYLIC ACIDS BY 3,692,810 9/1972 Washecheck.... -60/413 gtgz gg OXDATION OF FOREIGN PATENTS OR APPLICATIONS a. 2,165,858 7/1973 Germany 260/413 [75] inventors: Hans Schmidt; Werner Strabberger, 2,262,130 7/1974 Germany 260/413 both of Gersthofen, Germany [73] Assignee: Hoechst Aktiengesellschaft, Primary Examinerwinston A, Douglas Frankfurt am Main, Germa y Assistant ExaminerP. E. Konopka [22] Filed: Aug- 19, 1974 Attorney, Agent, or FirmConno1ly and Hutz 121] App]. No.: 498,567

[57] ABSTRACT [30] Forelgn Application Pnon y Data In the oxidation of higher a-olefins by means of chr0- Aug. 24, 1973 Germany 2342823 mosulfuric acid the Corresponding Saturated higher aliphatic monocarboxylic acids are obtained in a high [52] US. Cl. 260/413 yield if the Oxidation is carried out in the presence of [51] Int Cl 2 CllC l/00 58 F. I a iii. u I I u I I a o s I Q l I llld R 2 l 0 can: monoor dialcohols having from 10 to 40 carbon atoms. The carboxylic acids obtained are suitable for [56] uNlTEfi gg lfgs gziENTs preparing wax-like substances.

2,450,858 10/1948 Fitzpatrick 260/413 2 Claims, N0 Drawings PROCESS FOR PREPARING I-IIGI-I MOLECULAR WEIGHT ALIPHATIC CARBOXYLIC ACIDS BY CHROMOSULFURIC ACID OXIDATION OF a-OLEFINS The present invention relates to a process for preparing high molecular weight, aliphatic monocarboxylic acids.

The preparation of high molecular weight aliphatic monocarboxylic acids by oxidizing a-olefins having from 16 to 70 carbon atoms in the molecule or technical mixtures of such olefins by means of chromosulfuric acid is known (cf. German Offenlegungsschrift No. 2,165,858). According to this process colourless, thermostable fatty or wax acids are obtained containing, however, a considerable proportion of unreacted starting material. It is moreover known that this proportion may be materially reduced by carrying out the oxidation in several steps (cf. German Offenlegungsschrift No. 2,262,130). In the first step at least 50% by weight of the required quantity of chromosulfuric acid is used, the consumed oxidation agent is then separated and the oxidation is terminated in one or several further steps.

It has now been found that the proportion of unreacted olefin may be further reduced surprisingly by using a-olefins of a-olefin mixtures diluted with small quantities of higher, aliphatic alxohols.

The present invention provides a process for preparing saturated, high molecular weight, aliphatic monocarboxylic acids by oxidizing a-olefms having from 16 to 70 carbon atoms in the molecule or mixtures of such a-olefins in the molten state by means of aqueous chromosulfuric acid, which comprises adding to the molten olefins or mixtures of olefins prior to oxidizing of from 2 to 15% by weight, calculated on the olefins, of aliphatic monoor dialcohols having from to 40 carbon atoms in the molecule-optionally in the form of their fatty acid esters and then oxidizing with aqueous chromosulfuric acid.

According to the process of the invention the proportion of neutral matter in the oxidation products, depending on the quantity of chromosulfuric acid and the oxidation method used, may be reduced by 10 to 50% or even more.

Suitable starting materials for the chromosulfuric acid oxidation according to the invention are for example a-olefins having more than carbon atoms in the molecule, for example l-hexadecene, l-octadecene and l-eicosene or a-olefins having up to about 70 carbon atoms, which may be prepared by oligomerizing ethylene. Commercial mixtures of a-olefins having from 22 to 28 or from 24 to 48 carbon atoms are preferably used.

Especially suitable aliphatic alcohols are saturated monoalcohols having from 10 to 40 carbon atoms, preferably straight chain primary alcohols, as for example decyl alcohol, dodecyl alcohol, tetradecyl alcohol, cctyl alcohol and especially stearyl alcohol and behenyl alcohol, moreover glycoland polyglycol monoalkyl ethers having higher alkyl groups, such as the etheralcohol glycol-monostearyl ether. Synthetic monoalcohols, for example those, prepared according to the known polyethylene synthesis with Ziegler catalysts followed by oxidative hydrolysis of the aluminium trialkyls are also suitable. Aliphatic dialcohols having from 10 to 40 carbon atoms, for example a,w-diols, such as l, l0-decane-diol or 1,19mondecane-diol, and optionally polyalkylene glycols are also suitable; it should be taken into consideration however that dicarboxylic acids are generally formed in the oxidation of diols, so that the use of diols is not recommended, if the acids resulting from the oxidation shall be free from dicarboxylic acids. Esters of higher monoalcohols or diols with fatty acids having 2,3 or from 16 to 40 carbon atoms, for example stearyl acetate, stearyl stearate and esters of the montanic acid are also suitable. They are first saponified under the oxidation conditions, so that their efficiency finally is based on the presence of the basic alcohols.

The aliphatic monoalcohols or diols are added to the molten a-olefin or a-olefin mixture to be oxidized in an amount of from 2 to 15, preferably of from 4 to 10 by weight, calculated on the olefins.

The oxidation is carried out in known manner. Chromosulfuric acid containing per liter from 50 to 140 g of CrO preferably from to 120 g and from 300 to 650 g, preferably from 400 to 550 g of H 80 is used as oxidizing agent. The oxidation temperature is in the range of from 60 to 180C, preferably of from to 120C. The quantity of oxidizing agent required is from to 250 preferably from to 200 of CrO calculated on the weight of the olefin-alcohol mixture to be oxidized.

The oxidation is preferably carried out as follows: The molten olefin-alcohol mixture is introduced into the chromosulfuric acid heated to the desired oxidation temperature by small amounts or continuously and the mixture is vigorously stirred during the whole reaction. It is also possible to add the oxidizing agent to the molten mass of the product to be oxidized. According to a preferred method the reaction is carried out in a multiple-stage process, while separating the depleted oxidant after each step. The oxidation times are generally in the range of from 4 to 8 hours.

As soon as the reaction is terminated, which may be determined by titration of the residual CrO stirring is stopped and the reaction mixture is cooled, whereby the oxidation product and the used up oxidant separate into two layers. The carboxylic acid phase is washed while stirring with diluted sulfuric acid at a temperature of from 90 to 100C until it is free from chromium lll salt and is then washed with water at the same temperature until it is free from sulfuric acid.

The high molecular weight, aliphatic carboxylic acids or carboxylic acid mixtures obtained having a relatively low content of neural matter are colourless and thermostable and are especially suitable for preparing waxlike esters, partial esters and amides, which may be used as lubricants in the plastics processing and in the preparation of floor waxes and polishing pastes.

The following examples illustrate the invention.

EXAMPLES 100 g each of a commercial mixture of a-olefins having from 24 to 28 carbon atoms were mixed in the molten state with variable amounts of higher, aliphatic monoor dialcohols and oxidized with chromosulfuric acid containing per liter 100 g of CrO and 540 g of H 80 while stirring at a temperature of from 110 to l 15C. The quantity of CrO was in the range of from to by weight, calculated on the olefmalcohol mixture used (1.18 or 1.65 liter). in examples 1 and 2 the whole quantity of chromosulfuric acid was first introduced, whereas the oxidation was carried out in a two-stage process in examples 3 and 4, with separation of the oxidant used up in the first stage. The test dates and the results are listed in the following table.

lated on the olefins, of saturated aliphatic monoor dialcohols having from to carbon atoms in the Exquantity of chromosulfuric Oxidation ample alcohol added acid by weight) product by weight) total first second acid neutral stage stage number matter y weight) a 125 125 0 80 38.0 b 2.5 decyl 125 125 0 74 22.9 1

c 5.0 stearyl 125 125 0 77 27.6 d 5.0 C 125 125 0 74 27.2

a 175 175 0 92 34.3 b 5.0 decyl 175 175 0 80 26.2 2

c 5.0 stearyl 175 I75 0 84 21.4 d 10.0 stearyl 175 175 0 88 20.0 a 125 75 50 86 25.9 3 b 5.0 decyl 125 75 50 78 22.2 c 5.0 stearyl 125 75 50 83 23.2 a 175 125 50 1 13 19.5 b 2.5 decyl 175 125 50 93 16.7 c 5.0 decyl 175 125 50 96 10.4 4

d 5.0 stearyl 175 125 50 106 8.6 c 10.0 stearyl 175 125 50 106 10.2 f 10.0 diol" 175 125 50 113 7.8

synthelic alcohol, according to Ziegler, having 24 carbon atoms "aarnonadecane diol molecule, or their fatty acid esters, and then oxidizing with the aqueous chromosulfuric acid at a temperature of 60 to 180C.

2. The process as claimed in claim 1, wherein the aqueous chromosulfuric acid used is a chromosulfuric acid containing per liter of from 50 to g of CrO and from 300 to 650 g of H 50 

1. A PROCESS FOR PREPARING SATURATED, HIGH MOLECULAR WEIGHT, ALIPHATIC MONOCARBOXYLIC ACIDS BY OXIDIZING IN THE MOLTEN STATE A-OLEFINS HAVING FROM 16 TO 70 CARBON ATOMS IN THE MOLECULE OR MIXTURES OF SUCH OLEFINS BY MEANS OF AQUEOUS CHROMO-SULFURIC ACID, WHICH COMPRISES ADDING TO THE MOLTEN OLEFINS OR MIXTURES OF OLEFINS PRIOR TO OXIDIZING FROM 2 TO 15 % BY WEIGHT, CALCULATED ON THE OLEFINS, OF SATURATED ALIPHATIC MONO- OR DIALCOHOLS HAVING FROM 10 TO 40 CARBON ATOMS IN THE MOLECULE, OR THEIR FATTY ACID ESTERS, AND THEN OXIDIZING WITH THE AQUEOUS CHROMOSULFURIC ACID AT A TEMPERATURE OF 60* TO 180*C.
 2. The process as claimed in claim 1, wherein the aqueous chromosulfuric acid used is a chromosulfuric acid containing per liter of from 50 to 140 g of CrO3 and from 300 to 650 g of H2SO4. 